One vertex per element, one color per generator, with an edge from x to x·s.
(9,10)(11,18)(12,16)(13,15)(14,17)(19,24)(20,23)(21,22)(26,29)(27,28)(33,37)(34,36) involution — undirected(1,2)(3,5)(4,6)(7,8)(11,12)(16,18)(19,20)(23,24)(25,26,31,29)(27,32,28,35)(30,33,38,37)(34,39,36,40)(1,2,4,6)(3,5,7,8)(9,11,15,12)(10,16,13,18)(14,19,22,20)(17,23,21,24)(25,27,31,28)(26,32,29,35)(30,34,38,36)(33,39,37,40)(3,7)(5,8)(9,12,15,11)(10,16,13,18)(14,19,22,20)(17,24,21,23)(25,28,31,27)(26,32,29,35)(30,34,38,36)(33,40,37,39)(1,2)(3,5)(4,6)(7,8)(9,13,15,10)(11,16,12,18)(14,21,22,17)(19,23,20,24)(25,29,31,26)(27,32,28,35)(30,37,38,33)(34,39,36,40)(1,3)(2,5)(4,7)(6,8)(9,14)(10,17)(11,19)(12,20)(13,21)(15,22)(16,23)(18,24)(25,30,31,38)(26,33,29,37)(27,34,28,36)(32,39,35,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.